New concrete can repair its own cracks with bacteria

Used by the Roman Empire to construct their enduring architectural wonders, concrete has proven to be one of the most durable building materials. Though concrete reigns supreme, there is always room for improvement. For the past several years, a Dutch research team at Delft University of Technology has been working on a project to create a bio-concrete infused with the ability to self-repair. Led by scientists Henk Jonkers and Eric Schlangen, the team has recently unveiled the first application of its living concrete, which fills its cracks with the help of bacteria.

Jonkers originally began work on the bio-concrete when approached by a concrete technologist who wondered whether the safety of concrete could be improved using a biological solution. The cracks that form in concrete are not simply unsightly. “The problem with cracks in concrete is leakage,” says Jonkers. “If you have cracks, water comes through—in your basements, in a parking garage. Secondly, if this water gets to the steel reinforcements—in concrete we have all these steel rebars—if they corrode, the structure collapses.”

Although it only took Jonkers and his team three years to produce a prototype, their work was not without obstacles. “You need bacteria that can survive the harsh environment of concrete,” says Jonkers. “It’s a rock-like, stone-like material, very dry.” The team picked bacillus bacteria for its hardiness and longevity. The bacteria and its food source, calcium lactate, are packed into tiny capsules that dissolve when water enters the concrete cracks. Once released, the bacteria consume the calcium lactate, causing a chemical reaction that creates limestone, which then fills in the gaps.

A lakeside lifeguard station in the Netherlands is the site for the first application of bio-concrete. “We were really happy to see that it worked,” says Jonkers. “It is combining nature with construction materials,” he says. “Nature is supplying us a lot of functionality for free—in this case, limestone-producing bacteria. If we can implement it in materials, we can really benefit from it, so I think it’s a really nice example of tying nature and the built environments together in one new concept.”